MIT expert: Don't count on long-term success in climate policy

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Long-term climate change policy in the United States and abroad is likely to change very slowly, warns an MIT professor who says the lack of future flexibility argues for stronger short-term goals to reduce carbon emissions.

In a study in the current issue of Decision Analysis, a journal of the Institute for Operations Research and the Management Sciences, Assistant Professor Mort Webster of MIT's Engineering Systems Division tackles the complex problem of global climate change policy with a new approach.

Specifically, Webster's analysis incorporates the theory of "path dependency." In its most basic form, the theory holds that how something evolves in the future depends heavily on the path it was on in the past.

Webster says that because policy-making for climate change involves sequences of decisions over very long time periods, it is possible to reduce uncertainty and revise decisions along the way. But political systems can exhibit path dependency, a force that makes large policy shifts in the future difficult and rare, so most future decisions may only offer relatively small, incremental changes.

"Although staging climate change policy decisions over time would seem to make sense, the tendency of U.S. and international policy to change extremely slowly requires front-loading the painful decisions," Webster says, arguing that greater near-term emissions reductions are needed as a hedge against long-term catastrophe.

Webster challenges the Bush administration, which has cited uncertainty about future climate change among the reasons that it calls for the postponement of stricter mandated emissions reductions until the next decade.

The White House approach raises central questions for near-term climate policy, both in the United States and abroad, he writes: whether or not regulations of greenhouse gas emissions can be delayed, and whether some level of mitigating effort is required at once. Countering those who say the dust should settle before committing to big decisions, he points out that when a decision will be irreversible - as is likely the case in climate policy - delaying the decision is probably not the best option, according to research in decision analysis.

Decision-making in public policy, he writes, is complicated by the reluctance of leaders to reverse course after they have made important policy choices.

"A large-scale international policy issue such as climate change is especially vulnerable to path dependencies. If significant global emissions reductions are required in the long-run, this will be an extremely difficult problem to coordinate across nations," he writes.

Climate policy optimization models typically assume that some fraction of baseline emissions can be reduced in each period, ranging from none to nearly 100 percent, he notes. But, he notes, the range of reductions considered in any period is independent of any choices made in previous periods.

"The question posed in this study is: Does accounting for path dependency in political systems change the first-period (today) optimal choice from a sequential decision model of climate policy?" he writes. " If it does, then this would argue for a more aggressive hedging strategy with greater emissions reductions for near-term climate policy. This action would allow for greater flexibility if significant reductions are required later in the century."

Note: This text was adapted from a news release originally issued by the Institute for Operations Research and the Management Sciences.